1. Field of the Invention
The present invention relates to a liquid eject apparatus equipped with a liquid eject head for ejecting liquid and relates to an eject recovery method of the liquid eject head.
2. Brief Description of the Related Art
An ink-jet printer, a typical example of liquid eject apparatuses, widely known as an image forming apparatus, is generally equipped with an eject recovery device for removing thickened ink, foreign particles and the like stuck to a liquid eject portion of its recording head so as to keep a stable ejecting performance of the ink-jet printer. As shown in FIG. 8 for example, the eject recovery device comprises one or a plurality of caps 2 for covering a liquid eject portion 5a of a recording head 5 during non-printing operations to prevent ink as a liquid for recording from drying or evaporating and a pump 4 for sucking the thickened ink from and around the liquid eject portion 5a via the cap 2.
The above-mentioned eject recovery device is for example, arranged at a pre-determined standby position apart from a recording movement area of the recording head 5 of the ink-jet printer so as to face the recording head 5. The recording head 5, for example, is arranged below an ink cartridge 1 detachably mounted on a carriage (not shown in FIG. 8).
The pump 4, for example as also shown in the Japanese laid open patent No. 10-67121, comprises a cylinder connected to the inside of the cap 2 via a connecting tube 11 and a piston (not shown in FIG. 8) which reciprocally moves along an inner circular surface of the cylinder in a direction depicted by a bilateral horizontal arrow in FIG. 8 so as to generate a pre-determined negative pressure in the cap 2. Ink is sucked from and around the liquid eject portion 5a of the recording head 5, when the pump 4 is operated as the cap 2 is kept contacting closely to the liquid eject portion 5a of the recording head 5.
The cap 2 is held by a cap holder 3 rotatably supported by a cam surface formed on a cap cam 9 so as to move in directions depicted by a arched bi-directional arrows in FIG. 8, so that cap 2 selectively can be attached closely to the liquid eject portion 5a of the recording head 5 as depicted in two-dot chain lines in the figure, or can be detached from the liquid eject portion 5a of the recording head 5 as depicted respectively in solid lines in the figure.
The rotating movement of the cap holder 3 is controlled in accordance with a shape of the cam surface formed on the cap cam 9 which transmits a driving force from a driving power source to a supporting mechanism of the cap holder 3 at predetermined timings. The reciprocating movement of a piston rod 6 is controlled in accordance with a shape of the cam surface formed on a pump cam 7 which transmits the driving force from the driving power source to the piston rod 6 at predetermined timings.
The eject recovery treatment is executed according to the following operating procedures. The cap cam 9 is driven so that the cap 2 held in the cap holder 3 is moved from a pre-determined position and attached closely to the recording head 5. From a pre-determined initial position, the piston (not shown in FIG. 8) is moved reciprocally in accordance with synchronous movements of the piston rod 6 driven by the synchronously moving pump cam 7 so that a predetermined amount of ink is sucked from the recording head. Then the cap 2 is detached from the liquid eject portion 5a of the recording head 5 and returned to the initial position. Simultaneously the piston is moved to a predetermined position and is moved reciprocally for discharging ink filled in the inside of the cap 2 and the pump 4. Finally the piston is returned to the initial position. Thus a series of operations are executed continuously.
When a plurality of color ink tanks are mounted on the recording head 5 equipped with a color cartridge where a plurality of nozzle rows for respective colors or a plurality nozzle groups for respective colors arranged on one nozzle row, usually caps for respective colors are not arranged, but one or smaller number of caps than color number to cover a plurality nozzle rows or nozzle groups are arranged so as to simplify a sucking mechanism and reduce a production cost of the liquid eject apparatus.
However, in the above-mentioned conventional examples, a plurality of inks mix each other and form a turbid ink which fill the inside of the cap, when the sucking operation is executed. Even after the cap is detached from the liquid eject portion of the recording head, the remaining turbid ink stuck to the liquid eject portion is mixed with ink inside nozzles. Which causes a problem the so called xe2x80x9cmixed color phenomenonxe2x80x9d such that light colors such as yellow and the like are contaminated by the remaining turbid ink, when information is recorded on a recording medium.
As a measure trying to prevent the mixed color phenomenon, the turbid ink is ejected from the nozzles by executing pre-ejection, after a series of operations and a succeeding detaching operation of the cap from the recording head are finished, but before a recording operation is started.
However owing to ink properties and other various conditions a problem that the pre-determined amount of pre-ejection is not enough to eject mixed ink completely, is remained unsolved, consequently a fairly amount of ink has to be wasted for the pre-ejection in the following cases: (1) A large amount of ink remains in the recording head after detaching the cap from the recording head; (2) A large negative pressure (holding pressure) inside of the ink tank mounted on the recording head causes the more aggravated xe2x80x9cmixed color phenomenonxe2x80x9d due to a large amount of mixed ink flowing into nozzles.
The present invention is carried out in view of the problems mentioned above so as to provide an image forming apparatus and an image forming method which can solve problems such that a large amount of pre-ejected ink is consumed for preventing the mix color phenomenon and the like.
The following constitutions according to the present invention can solve the above-mentioned problems.
(1) A liquid eject apparatus comprising: a cap for capping a liquid eject portion for ejecting liquid, where: liquid is ejected from the liquid eject portion while the cap and the liquid eject portion are relatively moving from a closely attached state to a detached state.
(2) A liquid eject apparatus comprising: a liquid eject portion for ejecting liquid; a cap for capping the liquid eject portion; and a sucking means for sucking liquid from the liquid eject portion via the cap, where: after sucking by the sucking means is finished, liquid is ejected from the liquid eject portion while the cap and the liquid eject portion are relatively moving from a closely attached state to a detached state.
(3) The liquid eject apparatus according to (2), where: after sucking by the sucking means is executed, ejecting liquid from the liquid eject portion is started while the relative movement is started when a pressure inside the cap returns to almost atmospheric pressure.
(4) The liquid eject apparatus according to (2), where: after sucking by the sucking means is executed, ejecting liquid from the liquid eject portion is started before a pressure inside the cap returns to almost atmospheric pressure; and then the relative movement is started.
(5) The liquid eject apparatus according to (2) or (3), where: sucking by said sucking means is executed again as said cap and the liquid eject portion are mutually being detached.
(6) The liquid eject apparatus according to (5), where: a gap formed between the cap and the liquid eject portion during the detached state is set between 0.1 mm and 1.5 mm.
(7) The liquid eject apparatus according to (5), where: sucking by the sucking means is executed again before ejecting liquid from the liquid eject portion is finished.
(8) The liquid eject apparatus according to (1) or (2), where: ejecting liquid from the liquid eject portion during the relative movement is executed against the cap.
(9) The liquid eject apparatus according to (1) or (2), where: the cap is capping a plurality of the liquid eject portion, which respectively eject different liquids, altogether.
(10) The liquid eject apparatus according to (1) or (2), where: the liquid eject portion is equipped with electro-thermal conversion modules to generate thermal energy utilized for ejecting liquid.
(11) An eject recovery method comprising steps of: relatively moving a liquid eject portion for ejecting liquid and a cap for capping the liquid eject portion from a closely attached state to a detached sate; and ejecting liquid from the liquid eject portion; where: both moving and ejecting steps are executed concurrently.
(12) An eject recovery method comprising steps of: sucking liquid from a liquid eject portion for ejecting liquid while a cap for capping the liquid eject portion caps the liquid eject portion; relatively moving the liquid eject portion and the cap from a attached state to a detached sate; and ejecting liquid from the liquid eject portion; where: both moving and ejecting steps are executed concurrently.
(13) The eject recovery method according to (11), where: after sucking liquid from the liquid eject portion, ejecting liquid from the liquid eject portion is started when a pressure inside the cap returns to almost atmospheric pressure.
(14) The eject recovery method according to (11), where: after sucking by the sucking means, ejecting liquid from the liquid eject portion is started before a pressure inside the cap return to almost atmospheric pressure; and then the relative movement is started.
(15) The eject recovery method according to (11) or (12), where: sucking by the sucking means is executed again as the cap and the liquid eject portion are mutually being detached.
(16) The eject recovery method according to (15), where: a gap formed between the cap and the liquid eject portion during the detached state is set between 0.1 mm and 1.5 mm.
(17) The eject recovery method according to (15), where: sucking by the sucking means is started again before ejecting liquid from the liquid eject portion is finished.
(18) The eject recovery method according to (11) or (12), where: ejecting liquid from the liquid eject portion during the relative movement is executed against the cap.
(19) The eject recovery method according to (11) or (12), where: the cap is capping a plurality of the liquid eject portion, which respectively ejecting different liquids, altogether.